The goal of this grant is to generate new mouse models for human diseases of the elastic fiber system. Quantitative and qualitative changes in the extracellular elastic fiber network are known to be associated with a range of congenital and degenerative conditions affecting the cardiovascular, pulmonary, skeletal, ocular and cutaneous systems. The extracellular matrix protein fibulin-4 has recently emerged as a molecule that is essential for elastic fiber assembly. This protein interacts with tropoelastin and fibrillin-1, and its deficiency results in impaired elastic fiber formation and increased TGF-2 signaling in mice. Recently, missense mutations in fibulin-4 have been identified in human patients with clinical manifestations of aortic aneurysm, pulmonary artery stenosis, tortuous arteries, emphysema, congenital bone fractures, joint laxity and cutis laxa. These findings suggest that fibulin-4 is pleiotropic with widespread effects, and that amino acid variations in fibulin-4 may be risk factors for complex diseases, such as aneurysm, emphysema and osteoporosis. This application proposes to generate two mouse models harboring different missense fibulin-4 mutations recently identified in patients. The missense mutations will be introduced into mouse embryonic stem cells, which will be used to generate heterozygous and then homozygous mouse mutants. These models will facilitate a deeper understanding of the molecular basis and pathogenesis of diseases resulting from fibulin-4 missense mutations. The mouse mutants can be bred with mouse models of other elastic fiber components in the future, thereby enabling studies of differential and overlapping functions served by fibulin-4 and other key elastic fiber components. The mouse models will also provide novel insights into the etiology and pathogenesis of complex diseases associated with elastic fiber dysfunction. Availability of these mouse models is central to the evaluation of therapeutic strategies for elastic fiber diseases. PUBLIC HEALTH RELEVANCE: This application proposes to generate mouse models for human diseases of the elastic fiber system. Defects in elastic fibers of the connective tissue can result in aortic aneurysm, lung emphysema, bone fractures and loose skin. Generation of mouse models is central to the development of therapeutic treatment for these disorders.